NAME
Moos - Moo s{imple,peedy,ingle}
SYNOPSIS
package Foos;
use Moos;
extends 'Boos';
has this => ();
has that => 42;
has other => (
builder => 'build_other',
lazy => 1,
);
sub BUILD {
my $self = shift;
# build, build, build
}
sub BUILDARGS {
my ($self, @args) = @_;
# munge, munge, munge
return {%munged_args};
}
DESCRIPTION
Moos completes the M to Moose sequence of Perl OO modules.
This one is pure Perl, no dependencies, single file and Moose compatible
(for what it does).
FEATURES
Here's a quick list of the Moose compatible features that are supported
by Moos:
strict / warnings
Turns on "strict" and "warnings" for you.
extends
For inheritance. "Moos::Object" is the default base class.
package MyClass;
extends 'MyBaseClass';
Supports multiple inheritance, by allowing multiple classes on a
single invocation.
new A constructor class method.
my $object = MyClass->new(this => 'nice', that => 2);
BUILD
Custom object construction. If you define BUILD, it is passed the
value of the new object during construction. You can modify the
object. Any value you return is ignored.
sub BUILD { my $self = shift; ... }
Helpful exports
The ever useful "blessed" (from Scalar::Util) and "confess" (from
Carp) are exported to your namespace.
has Accessor generator. Supports the "is", "default", "build", "lazy",
"clearer", "predicate", "required" and "handles" options, described
below.
has this => ();
NOTE: Class::XSACcessor will be used for simple accessors if it is
installed. This can be disabled by setting $Moos::CAN_HAZ_XS to
false or by setting the PERL_MOOS_XS_DISABLE to true.
is Specify which type of attribute accessor to provide. The default is
"rw", a read-write accessor. Read-only "ro" accessors are also
supported.
has this => ( is => "ro" );
default
Specify the sub to generate a default value.
has this => ( default => sub { 42 } );
builder
Specify the method name to generate a default value.
has this => ( builder => '_build_this' );
has that => ( builder => 1 ); # accept default name for method
lazy
Don't generate defaults during object construction.
has this => ( builder => '_build_this', lazy => 1 );
clearer
Creates a clearer method.
has this => ( clearer => "clear_this" );
has that => ( clearer => 1 ); # accept default name for method
predicate
Creates a predicate method, which can be used to check if the
attribute is set or unset.
has this => ( predicate => "has_this" );
has that => ( predicate => 1 ); # accept default name for method
required
Require that a value for the attribute be provided to the
constructor or generated during object construction.
has this => ( required => 1 );
handles
Delegated method calls.
has wheels => (handles => [qw/ roll /]);
This accepts a hashref or arrayref, but not the other possibilities
offered by Moose.
Note that currently all accessors are read-write by default and all
unknown options are silently ignored.
HAS DIFFERENCES
Moos has a few differences from Moose, regarding it's accessor support
(ie the 'has' function).
The supported options detailed above are about the same as Moose. All
other arguments are currently ignored. All generated accessors are 'rw'.
So you can just say:
has 'this';
has that => ();
Unlike the other Mo* modules, Moos also supports just specifying the
default. If the number of arguments (after the name) is an odd number,
then the first value is the default. The following forms are valid:
has a => 42;
has b => 'string' => (lazy => 1);
has c => {};
has d => [1, 2, 3, 4];
These all result in creating a Moos "default" argument. If the default
is an array or hash reference, a shallow copy is made.
DEV OPTIONS
Moos has a couple builtin dev options. They are controlled by
environment variables.
PERL_MOOS_ACCESSOR_CALLS
By setting this environment variable, Moos will warn everytime an
accessor method is called.
PERL_MOOS_XXX
By setting the environment variable, Moos will export the XXX
debugging keywords.
WHENCE
I(ngy) created Moos during Pegex development. Pegex uses a clone of Moos
called Pegex::Base.
Pegex is a parser framework and needs to be fast. While looking into
speed issues I noted that accessor calling was the biggest hit. I tried
all the various Mo* solutions and Mouse was the fastest.
I was happy until I remembered that Mouse uses XS, and for various
reasons this broke my toolchain (TestML, Module::Install, etc).
I tried to inline Moo into one file but failed, and ended up with this.
I've shared Pegex::Base as Moos in case any other projects want it.
Later on, Toby added a bunch of low-cost but very handy features from
Moose.
ON SPEED
In the end, I got Pegex to run even faster with Moos than it originally
did with Mouse. I'll tell you my secret...
Replace these:
my $foo = $self->foo;
$self->foo($foo);
with:
my $foo = $self->{foo};
$self->{foo} = $foo;
And your code will be faster (and a bit uglier).
The only time that you need to call an accessor method is when you are
reading a property and it might invoke a "lazy" "builder" or "default"
method. Otherwise you are just wasting time. At least with the minimal
feature set offered by Moos.
The PERL_MOOS_ACCESSOR_CALLS feature described above is for finding
these method calls.
Note that users of your module's accessor methods can still use the
method calls like they would expect to.
I'm sure I've missed some subtlties, and would be glad to hear opinions,
but in the meantime I'm happy that my code is faster and pure Perl.
SEE ALSO
* M
* Mo
* Moo
* Moos
* Moose
* Mouse
* Mousse
AUTHORS
Ingy döt Net
Toby Inkster
COPYRIGHT AND LICENSE
Copyright (c) 2012. Ingy döt Net.
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
See http://www.perl.com/perl/misc/Artistic.html